The purpose of this research was to collect information concerning the systems which hospitals have developed to monitor and report adverse drug events (ADE). In addition, the attitudes and perceptions of those coordinating the program toward postmarketing surveillance of such events were investigated. The sample was stratified by hospital size. Questionnaires were sent to 725 Joint Commission for Accreditation of Health Care Organization accredited hospitals (30.5 small, 27.5 medium, and 14.5 large). Completed questionnaires were received from 306 respondents, representing a 42% overall response rate. Differences among the three groups were seen in the professional personnel involvement in the monitoring activities, reporters of ADEs, and dissemination of ADE information. Pharmacists had the biggest role in implementing this function and concurrent review methods generated the greatest percentage of ADEs. Overall, the systems were similar among hospitals of different sizes.